USE OF CONTROLLED RELEASE PHOSPHATIC FERTILIZER TO IMPROVE GROWTH, YIELD AND PHOSPHORUS USE EFFICIENCY OF WHEAT CROP

Transcription

1 Pk. J. Agri. Si., Vol. 54(4), ; 2017 ISSN (Print) , ISSN (Online) DOI: /PAKJAS/ USE OF CONTROLLED RELEASE PHOSPHATIC FERTILIZER TO IMPROVE GROWTH, YIELD AND PHOSPHORUS USE EFFICIENCY OF WHEAT CROP Soi Noor 1,*, Muhmm Yseen 1, Muhmm Nvee 1 n Rshi Ahm 2 1 Institute of Soil n Environmentl Sienes, University of Agriulture-38040, Fisl, Pkistn; 2 Deprtment of Agronomy, University of Agriulture-38040, Fisl, Pkistn. * Corresponing uthor s e-mil: soi_noorr@yhoo.om Phosphorus (P) use effiieny is very low (5 to 25%) ue to fixtion with C +2 /Mg +2 in lkline/lreous soils whih ereses P vilility for plnt uptke. There is nee to improve P vilility for plnt growth. For this purpose, oting of phosphti fertilizer with the orgni polymer my reue P fixtion n use the stey relese of P to inrese its use effiieny. This stuy esses enhne phosphorus use effiieny long with improve growth of whet t ifferent rtes of polymer ote i-mmonium phosphte (DAP) in omprison with unote DAP. In lortory experiments, relese pttern of P in soil from ifferent oting onentrtions (0, 0.5, 1.0, 1.5%) n numer of otings (unote, single, oule, triple) were teste uner ontrolle onitions. The est sreene polymer onentrtion (1%) n oting lyers (oule oting) were teste uner fiel onitions on whet rop growth, yiel n fertilizer effiieny. Results showe tht pplition of of reommene rte of P s polymer ote DAP inrese plnt height (4%), iologil yiel (39%), grin yiel (29%), gronomi effiieny (58%), reovery effiieny (130%) n nitrogen, phosphorus n potssium ontents of whet grin n strw ws lso inrese ompre to unote DAP. These results revele tht polymer ote DAP n e prove more effetive fertilizer to improve growth, yiel n phosphorus use effiieny of the whet rop over ommeril DAP. Keywors: Agronomi effiieny, polymer, reovery effiieny, yiel, phosphti fertilizer INTRODUCTION Soil nutrient mngement t suffiient level is importnt for mintining high qulity n sustinle rop proution. Exogenous fertilizer pplition is n instnt soure of nutrient replenishment. Mny types of reserh revele tht ommeril hemil fertilizers inrese 30 to 50% rop yiel (Stewrt et l., 2005). The replenishment of nutrients is usully rrie out y the introution of orgni n inorgni sustnes suh s soil menments, mnures, orgni or hemil fertilizers (Timilsen et l., 2015). The minerl fertilizers re pplie to inrese rop yiels ut the min limittion in hieving the rop potentil is limite use of pplie fertilizers prtiulrly P y rop ompre to other fertilizers. Avilility of P in soils of Pkistn is very low; out 90% soils suffer from equte to severe P efiieny (NFDC, 2003). From pplie fertilizer, only smll mount of it goes to soil solution tht my e either tken up y rops or preipittes in soil (Leytem n Mikkelsen, 2005). Soil nutrient efiieny n e fulfille to gret extent y the pplition of pproprite fertilizer type, pplition rte, n metho of pplition (Timilsen et l., 2015). But ue to the high ost of fertilizers, these re not profitle to frmers (Shheen et l., 2004). Unvilility of P from pplie phosphti fertilizers to plnts ue to fixtion with soil onstituents n e prevente y using numer of tehniques inluing i pplition, n plement of phosphti fertilizers, the ition of orgni mtter, miroil inoultion n io-fertilizers (Trolove et l., 2003). But still, P vilility of pplie fertilizer is ig issue in lmost ll soils. The effiieny of pplie phosphti fertilizers uner ll irumstnes is not exeeing 25%. Commerilly ville fertilizers re proving insuffiient for sustinle rop proution. To hieve yiel gols it is neessry to improve the pplie fertilizer s feture y oting with suitle mteril. Tht woul inrese its use effiieny in suh wy tht they shoul e le to proue higher yiel even t reue rte of pplition ompre to onventionl pplition of phosphti fertilizers (Trenkel, 2010). Polymer ote or ontrolle relese fertilizers (CRF) n e one of the est pprohes to improve phosphorus use effiieny (PUE) s these relese P oring to plnt emn. So less P is interting with soil, the ultimtely smll mount of P is ville for fixtion, whih in turn inrese use effiieny, reue negtive effets ssoite with overosge, reue rte of the pplition (Zhrni, 2000; Yseen et l., 2014, 2017). But the mteril use for oting shoul e eonomil n revel goo oting property. However, most of the ville polymer is more expensive n inrese the proution ost long with environmentl prolems. So, there is nee to hoose ost effetive oting mteril. Therefore, the present stuy is fousing on the

2 Noor, Yseen, Nvee & Ahm sreening of polymer onentrtions n numer of oting lyers on phosphti fertilizers to prolong the vilility of P in the soil to meet the plnt requirements in fiel pplition for whet proution. MATERIALS AND METHODS Experimentl mteril for lortory stuies: Coting of the wter solule polymer on ommerilly ville DAP (immonium phosphte) (Yseen et l., 2017) ws rrie out in Soil Fertility n Plnt Nutrition L, Institute of Soil n Environmentl Sienes, University of Agriulture, Fisl. This oting ws one oring to polymer strength (0, 0.5, 1, 1.5%) in experiment 1 n oting thikness (unote, single, oule, triple) in experiment 2. Cote DAP fertilizer ws rie uner lortory onitions t mient temperture n store in polyethylene gs till pplition. The soil ws ollete from the lok llotte for fiel experiment t Reserh Are of Institute of Soil n Environmentl Sienes, University of Agriulture, Fisl, Pkistn. Soil of the experimentl site ws sny ly lom in texture with ECe 1.96 S m -1 (Rihrs, 1954), ph 7.7 (Prs et l., 2006), orgni mtter ontents 0.64% (Wlkey n Blk, 1934), totl N ontents 0.04% (Jkson, 1962), Olsen P 6.2 mg kg -1 soil (Olsen et l., 1954), extrtle K 115 mg kg -1 soil (Hnwys n Heiel, 1952) n CCO 3 5%. Disposle ups of 250 m 3 were use uring the stuy. Eh up ws fille with 200 g soil. Sturtion perentge of soil use ws etermine to mintin require moisture ontents in ups. Cote n unote DAP ws pplie (0.25 g P 100 g -1 of soil) in ups with respetive onentrtions oring to the tretment pln n mixe in soil thoroughly. Cups were ple rnomly in n inutor (Snyo; MIR 253) t 25+2 C temperture fter ition of istille wter to mintin moisture ontent t fiel pity n it ws mintine fter every 24 hours. Olsen P ws etermine fter ifferent time intervl (15, 30, 45 n 60 ys) y metho (Olsen et l., 1954). Results of the 1 st experiment propose the est polymer onentrtion while the 2 n propose the est numer of lyers to e ote on DAP fertilizer grnules. Fiel experiment: The experimentl pln for whet rop ws omprise of five tretments i.e. T 1 = Control (without ny fertilizers), T 2 = NK + P from unote DAP t reommene rte, T 3 = NK + P from polymer ote DAP t reommene rte, T 4 = NK + P from polymer ote DAP t 75% of reommene rte, T 5 = NK + P from polymer ote DAP t 50% of reommene rte. Rnomize omplete lok esign with three replitions ws use to ollet. Reommene rtes of fertilizers use for whet were N = 120 kg h -1, P 2O 5 = 90 kg h -1 n K 2O = 60 kg h -1. In ll tretments exept ontrol, reommene oses of N n K were e. Soures of fertilizers use were ure (46% N) for N, sulphte of potsh (50% K 2O) for K n i-mmonium phosphte (P 2O 5 46% n 18% N) for P. P n K fertilizers were pplie uring soil preprtion n N fertilizer ws pplie in three splits. One-thir of require N s per tretment requirement ws pplie efore sowing n remining N ws pplie in two splits t 25 n 45 ys fter germintion. Drill sowing of whet v. Fisl-2011 ws one n the rop ws five times irrigte with nl wter. One squre meter re ws rnomly selete in eh plot for mesuring growth n yiel ttriutes 20 ys efore hrvesting n verge vlues were ompute. At hrvest, grin n strw yiel ws reore for eh plot. The iologil yiel ws lulte y the formul given elow. Biologil Yiel =Totl iomss of plnts in the plot (grin+strw yiel) At vegettive stge (efore ooting stge) prmeter i.e. photosyntheti rte (A) n wter use effiieny were mesure y using CIRAS-3 (PP System, Amesury, MA, USA) with PLC3 universl lef uvette, mesuring oth sies of the fully expne upper lef. The uvette ws provie light vi light emitting ioes (LED) n with photon flux of 1000 μmol m -2 s -1, mient lef temperture n 390 μmol mol -1 CO 2. Chlorophyll ontent in flg leves ws mesure with the help of portle Chlorophyll Meter SPAD-501 efore grin formtion. Chemil nlysis for totl P uptke in whet: At hrvesting time, smples of grin n strw were rwn from eh plot of the experiment for the hemil nlysis of NPK onentrtion. Nitrogen n potssium ontents of hrveste smples were estimte y using metho (Chpmn n Prker, 1961). Phosphorus ws etermine on spetrophotometer t 420 nm wvelength y using sorne moe (Olsen et l., 1954). By the P ontent of strw n grin, phosphorus uptke (PU) y the whet plnt ws lulte y the formul: oven rie weight of plnt P (%) PU = 100 Totl P uptke=p uptke in grin+p uptke in strw Nutrient use effiienies: AE (g/g) = ARE (%) = Fertilize plnt iomss unfertilize plnt iomss Amount of fertilizer pplie uptke y fertilize plnt-uptke y unfertilize plnt Amount of fertilizer pplie 100 AE = Agronomi effiieny, ARE = Agronomi reovery effiieny Sttistil nlysis: Dt ws nlyze sttistilly oring to Fisher s nlysis of vrine (Steel et l., 1997). Mens were ompre y using HSD test t 5% proility level. RESULTS Phosphorus relese pttern in soil in response to ifferent onentrtions of polymer ote on DAP: Soil trete with 542

3 Polymer ote phosphti fertilizer unote immonium phosphte (DAP) showe the highest onentrtion of Olsen s P in the soil fter 15 ys of inution perio s ompre to DAP ote with ifferent onentrtions of polymer. At 30 ys of inution perio, erese in P relese in unote DAP fertilizer ws reore. Mximum P relese ws reore in DAP ote with 0.5% polymer onentrtion. Deresing tren in Olsen s P in soil in unote DAP tretment with the pssge of time inite mximum relese of P immeitely fter pplition of this fertilizer. Tretments of 1 n 1.5% polymer onentrtions on DAP fertilizer use inrese in P relese in soil with n inrese in numer of ys. At inution time of 45 ys, soils trete with unote DAP showe further erese in soil P onentrtion. Mximum P relese ws oserve in soil trete with 0.5 n 1% polymer ote DAP. However, DAP fertilizer ote with 1.5% polymer onentrtion showe inresing tren in P relese in soil ompre to their previous inution ys. At 60 ys of inution, no signifint relese of P ws oserve in the tretment of unote DAP fertilizer. Among oting onentrtions of polymer on DAP, 0.5% polymer onentrtion showe minimum P relese; even then this relese onentrtion ws greter thn unote fertilizer soures. DAP ote with 1% polymer onentrtion showe signifintly mximum ut t pr with 1.5% polymer onentrtion on P relese in soil t 60 ys of inution. Signifint ifferenes in Olsen s P onentrtions in soil trete with ote n unote DAP fertilizer soures t ifferent time intervls re shown in (Tle 1). On these results sis, 1% polymer onentrtion ws foun etter n selete for next experiment. Effet of numer of polymer lyers ote DAP on P relese in the soil: Sttistil nlysis of t relte to numer of otings of 1% polymer onentrtion (the est selete from experiment 1) on DAP fertilizer for the relese of phosphorus in soil showe signifint ifferenes in P relese pttern mong ote n unote DAP fertilizer over ifferent inution time perios (Tle 2). Sttistil nlysis of P relese with respet to inution time perio revele tht phosphorus vilility erese with inresing numer of oting lyers n ys thn unote phosphti fertilizer DAP, furthermore, unote DAP fertilizer trete soil h mximum relese P uring 15 ys of inution. With the pssge of time, P relese ws inrese from ote fertilizer ompre to unote fertilizer. At 30 ys of inution single ote DAP gve mximum P relese in soil, wheres fter 45 ys of inution oule lyer ote DAP relese mximum P. At 60 ys of inution, triple lyer polymer ote DAP showe n inrese in soil P onentrtion thn their previous inution time perios. From the results, it n e onlue tht oule lyer oting of polymer on DAP fertilizer inite mximizing tren of P relese in soil n lso mthe with plnt require ompre to ll other numer of otings s well s unote DAP. Fiel Experiment: Whet growth n yiel prmeters: Polymer ote DAP fertilizer pplition showe signifint effet on growth n yiel of whet over ommeril fertilizer use (unote DAP). However, signifint ifferene in whet plnt height ws oserve; reommene rte of polymer ote DAP n unote DAP inrese whet plnts height over ontrol i.e., 13.4 n 4.1%, respetively. All other rtes of polymer ote DAP hve lso inrese plnt height s ompre to ontrol (Tle 3). Polymer ote DAP pplition t rte of reommention inrese Tle 1. Relese of P in soil (mg P kg -1 soil) trete with ifferent onentrtions of polymer ote on DAP. Conentrtion of polymer Inution intervls (ys) Men ote on DAP fertilizer (%) Unote (Control) g i B g e A h f A k j e C Men D C B A Vlues shring sme letter o not iffer t p = 0.05 oring to HSD test. HSD vlues (ritil vlues for omprison): Men for ys (A) = 17.4, Men for polymer oting onentrtion (B) = 17.4, Intertion (A B) = Tle 2. Relese of P (mg P kg -1 soil) in soil trete with DAP ote with ifferent numer of polymer lyers. Numer of 1% polymer oting Inution intervls (ys) Men lyers on DAP Unote e h k C Single i f B Doule j e A Triple l j g D Men C B A A Vlues shring sme letter o not iffer t p = 0.05 oring to HSD test. HSD vlues (ritil vlues for omprison): Men for ys (A) = 13.8, Men for polymer oting lyers (B) = 13.8, Intertion (A B) =

4 Nutrient on in strw (%) Noor, Yseen, Nvee & Ahm Tle 3. Effet of polymer ote DAP on growth n yiel omponents of whet in fiel onitions. DAP pplition rte (s per Plnt height No. of fertile 1000 grin Yiel ttriute (kg/h) reommene rte) (m) tillers (m -2 ) weight (g) Grin yiel Biologil yiel Control e e 8080 e Unote DAP () Polymer ote DAP () Polymer ote DAP (75%) Polymer ote DAP (50%) HSD t Vlues shring sme letter o not iffer t p = 0.05 oring to HSD test. numer of tillers 23% ompre to unote DAP pplition (Tle 3) grin weight in the tretment of reommene rte of polymer ote DAP fertilizer inrese y 16% over reommene rte of unote DAP fertilizer pplition. Grin yiel kg h -1 s result of tretment of reommene rte DAP ote with polymer ws vrie sttistilly from ll other tretments n it ws 29% higher ompre to unote DAP fertilizer pplition. Moreover, pplition of 75% of reommene rte of polymer ote DAP improve 20% grin yiel ompre to unote DAP, respetively. The mximum inrese in iologil yiel ws oserve in tretment reeiving reommene rte of polymer ote DAP n tht ws 39% higher s ompre to unote DAP (Tle 3). Physiologil prmeters: Applition of reommene rte of polymer ote DAP inrese the hlorophyll ontents y 28 n 8% s ompre to ontrol n unote DAP, respetively (Fig. 1). Figure 1. Effet of polymer ote DAP on physiologil prmeters of whet uner fiel onitions ontrol un- DAP 75% 50% N P K Control = without ny fertilizer, Un-DAP = unote DAP with rte of reommene ose, = Polymer ote DAP t rte of reommene ose, 75% = Polymer ote DAP t 75% rte of reommene ose, 50% = Polymer ote DAP t 50% rte of reommene ose. Men vlues shring sme letter(s) o not iffer t p = 0.05 oring to HSD test. Figure 2. Effet of polymer ote DAP on N, P n K onentrtions (%) in strw of whet uner fiel onitions. Control = without ny fertilizer, Un-DAP = Unote DAP t of reommene ose, = Polymer ote DAP t of reommene ose, 75% = Polymer ote DAP t 75% of reommene ose, 50% = Polymer ote DAP t 50% of reommene ose. Men vlues shring sme letter o not iffer t p = 0.05 oring to HSD test. Similrly, signifint improvement in photosyntheti rte ws reore in the tretments of polymer ote DAP over ontrol n unote tretments. There ws 6.32 n 1.12% inrese in photosyntheti rte with the pplition of 100 n 75% of reommene rte of polymer ote DAP over unote DAP. With the inrese in photosyntheti rte wter use effiieny ws lso inrese (9.15%) in the tretment of polymer ote DAP fertilizer pplie t rte of reommention (Fig. 1). Effets of polymer ote DAP on N, P n K onentrtions in whet: Dt regring N, P n K onentrtion in strw n grin is given in Figure 2 n 3. With the pplition of 100 n 75% of reommene rte 544

5 Nutrient on in grin (%) Polymer ote phosphti fertilizer signifint inrese in nutrients onentrtion in plnt oy (strw + grin) ws reore over unote DAP fertilizer pplition. Thus, the highest NPK onentrtion in whet grin n strw ws ttine with pplition of of reommene rte of polymer ote DAP y 42, 47 n 25%, respetively in grin n 14, 39 n 25%, respetively in strw ontrol un- DAP 75% 50% N P K Control = without ny fertilizer,un-dap = unote DAP with rte of reommene ose, = Polymer ote DAP t rte of reommene ose, 75% = Polymer ote DAP t 75% rte of reommene ose, 50% = Polymer ote DAP t 50% rte of reommene ose. Men vlues shring sme letter(s) o not iffer t p = 0.05 oring to HSD test. Figure 3. Effet of polymer ote DAP on N, P n K onentrtions (%) in grin of whet uner fiel onitions. The results given in Figure 4 showe the impt of polymer ote DAP on the totl uptke of P (grin + strw). The mximum inrese in P uptke ws oserve in tretment with polymer ote DAP t reommention rte i.e. 116% over onventionl unote DAP pplition. Moreover, there ws 27 n 68% inrese in totl P uptke; y 75% n 50% of reommene rte of polymer ote DAP over unote DAP. Agronomi n reovery effiieny: Effets of polymer ote DAP on phosphorus use effiienies is reflete from the t given in Figure 4. Results showe tht gronomi n reovery effiieny of P ws inrese with eresing the rtes of polymer ote DAP fertilizer. The mximum inrese in P gronomi effiieny ws reore in the tretment of 50% of reommene rte of polymer ote DAP i.e. 112% higher thn unote DAP pplition. Similrly, mximum reovery effiieny ws oserve in polymer ote DAP t 50% rte of reommention followe y 75 n rte of reommention i.e. 172, 159 n 130% inrese over unote DAP pplition respetively (Fig. 4). 0 Plnt P uptke (kg/h) ontrol 2.60 Control = without ny fertilizer,un-dap = unote DAP with rte of reommene ose, = Polymer ote DAP t rte of reommene ose, 75% = Polymer ote DAP t 75% rte of reommene ose, 50% = Polymer ote DAP t 50% rte of reommene ose. Men vlues shring sme letter(s) o not iffer t p = 0.05 oring to HSD test. Figure 4. Effet of polymer ote DAP on P uptke, gronomi effiieny (AE) n reovery effiieny (RE) in whet rop grown uner fiel onitions. DISCUSSION e AE (kg grin/kg P pplie) RE (%) un-dap % % Phosphorus fertilizer use effiieny is quite low in soils of Pkistn n it rnges s low s 5% to s high 25% epening on fertilizer mngement strtegies. Its vilility in lkline n lreous soil is quite low ue to primry n seonry retion with C/Mg whih retrs P vilility. As phosphti fertilizers re too ostly, there is ire nee to improve the use effiieny of pplie phosphti fertilizer (Trenkel, 2010). Coting of phosphti fertilizers with the polymer is n innovtive option to improve phosphorus use effiieny n onsistent relese of P in the soil. Polymer ote fertilizers grully relese its nutrient ontents; orrespon to the plnt's requirement (Hnfi et l., 2000). These fertilizers re wter solule whih re ote with the mterils whih reue their issolution rte n fixtion in soil. Better effiieny, ue to slower n grul relese from ote 545

6 Noor, Yseen, Nvee & Ahm fertilizers, n e helpful in term of reue frequeny of pplition n lso minimize the negtive effets ssoite with over osge (Zhrni, 2000; Hopkins et l., 2008). Moreover, polymer ote phosphti fertilizer hve potentil to reue P fixtion n preipittion minly y holing the P omplex mking elements n sorption of wter to inrese its iffusion shell. The present stuies emonstrte the relese ptterns of P in soil from polymer ote DAP with ifferent onentrtions n numer of oting lyers fter tht the effet of polymer ote phosphti fertilizer (DAP) on growth; yiel n phosphorus use effiieny in whet rop ws evlute. It ws foun in lortory stuies tht polymer otings on DAP fertilizer with ifferent polymer onentrtion showe liner inrese in ville P up to 2 months. Phosphorus relese from DAP ws the mximum t 1% polymer onentrtion. The itionl enefits regring the seletion of 1% polymer onentrtion were tht less quntity of polymer use tht ultimtely reues the ost of polymer ote fertilizers n less effort require y miroes to egre tht polymer within the growing perio of rop plnts (Yseen et l., 2017; Yseen et l., 2014). Similrly, in next inutor stuy, DAP fertilizer with oule lyer of the polymer showe the highest ville P uring the stuy. The thikness of ote mteril on fertilizer grnules plys n importnt role in relesing of nutrient from polymer ote fertilizer. The relese rtes from two n three lyere ote mterils were reltively low ompre to single ote mteril. Cote fertilizers relese nutrients with the pssge of time n mintin the optimum level of phosphorus for plnt requirements (Shrm, 2006). The ooste grin yiel with pplition of polymer ote fertilizer is olletive enefit from improve ll yiel omponents like 1000-grin weight, the numer of grins per spike n numer of the fertile tiller. The superiority of polymer ote phosphti fertilizers ws proly ue to mintining the intimte vilility of P in the soil for eveloping root jent to fertilizer grnules. The importne of P for emerging rile n seminl roots uring seeling estlishment in whet might e responsile for higher numer of fertile tillers (Murphy n Sners, 2007). As P is iretly involve in grin formtion n evelopment, so its vilility throughout the growth perio improve numer n weight of grins n lso sve plnts from stress. Consistent supply of P uring growth perio of whet is ple of enhning growth n yiel ttriutes n polymer ote DAP hs ility to supply P for longer time thn unote DAP (Yseen et l., 2014, 2017). Polymer ote fertilizers pplition t reue reommene rte ws lso improve the P ontents of the plnt (strw n grin) resulte from higher P uptke, ue to the inrese vilility of P oring to the plnt requirement throughout the growing seson of the rop. There ws low hne for P fixtion in polymer ote fertilizers over unote phosphti fertilizer soures of minimum ontt with soil (Dunn n Stevens, 2008; Xing et l., 2008). Polymer ote DAP pplie t reue rtes resulte in higher PUE ue to the strong root ompetition n therey n effiient exploittion of pplie P. Similrly, with higher pplition rte of P, roots utilize the lower mount of P tht resulte in low PUE (Sners et l., 2012) The use of polymer ote fertilizers lso improve soil orgni mtter, n soil physil, hemil n miroil properties tht ultimtely ffet P nutrition of plnts (Yseen et l., 2017). The most enefiil effet of the polymer oting is tht it ontriutes towrs the use of less mount of phosphti fertilizer pplition tht ultimtely les towrs less ost of proution with inrese enefits. Conlusion: Mnipulting or ontrolling retions in the miroenvironment roun fertilizer grins hs een revele to hve importnt enefits to vilility of pplie nutrients. By this polymer tehnology, nutrients relese t slower rte throughout the seson, plnts re le to tke up most of the nutrients without wste y lehing. This tehnology not only hs prospetive to inrese prolong vilility of P, rop growth, yiels n frmer inomes y reuing its pplition rtes n losses. Aknowlegement: The reserh work in this mnusript is prt of the projet fune y Higher Eution Commission (HEC), Pkistn. Therefore, uthors re highly thnkful to HEC. REFERENCES Chpmn, H.D. n F. Prker Metho of nlysis for soil, plnt n wter. Div. Agri Univ. Cliforni, USA, pp Dunn, D.J. n G. Stevens Response of rie yiels to phosphorus fertilizer rtes n polymer oting. Crop Mnge. 7. oi: /cm rs Hnfi, M.M., S.M. Elti n M.B. Ahm Physil n hemil hrteristis of ontrolle relese ompoun fertilizer. Eur. Poly. J. 36: Hnwy, J.J. n H. Heiel Soil nlysis methos s use in Iow Stte College Soil Testing Lortory, Bulletin 57. Iow Stte College of Agriulture, USA; 131. Hopkins, B.G., C.J. Rosen n A.K. Shiffler Enhne effiieny fertilizers for improve nutrient mngement: Potto (Solnum tuerosum) rop mngement. Plnt Mngement Network. oi: /CM RV. Jkson, M.L Chemil omposition of soil. In: Ben F.E. (E.) Chemistry of soil. Vn Nostrn Co., New York, USA; pp Leytem, A.B. n R.L. Mikkelson The nture of phosphorus in lreous soils. Better Crops 89:

7 Polymer ote phosphti fertilizer Murphy, L. n L. Sners Improving N n P use effiieny with polymer tehnology. CCA Conf. Pro. Inin. NFDC Fertilizer Reommentions for Crops: Fertilizer Reommentions in Pkistn ( poket guie for extension workers). Ntionl Fertilizer Development Centre, Islm, Pkistn. Olsen, S.R., C.V. Cole, F.S. Wtne n L.A. Den Estimtion of ville phosphorus in soils y extrtion with soium ironte. Cirulr No. 939, USDA. US Government Printing Offie, Wshington, DC. Prs, R., Y.S. Shivy, D. Kumr n S.N. Shrm Lerning y oing exerises in soil fertility (A prtil mnul for soil fertility). Division of Agronomy, Inin Agriulturl Reserh Institute, Ini, New Dehli, 68. Rihrs, L.A Dignosis n improvement of sline n lkli soil. USDA Agri. Hnook 60, Wshington, D.C. Sners, J.L., L.S. Murphy, A. Nole, R.J. Melgr n J. Perkins Improving phosphorus use effiieny with polymer tehnology. Pro. Engin. 46: Shheen, N., M. Hussin, F. Yousf, M.S. Qureshi n S. Irees Effet of rhizoium strin on growth of two seseni spp. Pk. J. Soil Si. 2: Shrm, K.N.Sr Soil phosphorus frtion ynmis n phosphorus sorption in ontinous mize whet ropping system.18 th Worl Congr. Soil Si. July 9-15 Philelphi, Pennsylvni, USA. Steel, R.G.D., J.H. Torrie n D.A. Dikey Priniples n Proeures of Sttistis: A iometril pproh, 2 n E. MGrw Hill In., New York, USA. Stewrt, W.M., D.W. Di, A.E. Johnston, n T.J. Smyth The ontriution of ommeril fertilizer nutrients to foo proution. Agron. J. 97:1-6. Timilsen, Y.P., R. Ahikri, P. Csey, T. Muster, H. Gill n B. Ahikri Enhne effiieny fertilizers: A review of formultion n nutrient relese ptterns. J. Si. Foo Agri. 95: Trenkel, M.E Slow- n ontrolle-relese n stilize fertilizers: An option for enhning nutrient use effiieny in griulture. Interntionl Fertilizer Inustry Assoition (IFA): Pris, Frne. Trolove, S.N., M.J. Heley, G.J.D. Kirk, N.S. Boln n P. Lognthn Progress in selete res of rhizosphere reserh on P quisition. Aust. J. Soil S. 41: Wlkey, A.J. n I.A. Blk A ritil exmintion of rpi metho for etermining orgni ron in soils: Effet of vritions in igestion onitions n of inorgni soil onstituents. Soil Si. 37: Xing V., J.J. Yun, H. Ping n L.M. Zo Reent vnes on the tehnologies to inrese fertilizer use effiieny. Agri. Si. Chin 7: Yseen, M., M.A.F. Bjw, W. Ahme, S. Noor n M.A. Khli Improving growth, yiel n phosphorus use effiieny of whet y using smrt fertilizer evelope t UAF. Pper presente n strt pulishe in the Interntionl Conferene of Plnt Siene (ICPS) orgnize y GC University, Lhore, Pkistn from Septemer, Yseen, M., M.Z. Aziz, A. Mnzoor, Y. Hmi, S. Noor, M.A. Khli n M. Nvee Promoting growth, yiel n phosphorus use effiieny of rops in mizewhet ropping system y using polymer ote immonium phosphte. Comm. Soil Si. Plnt Anl. 48: Zhrni, S Utiliztion of polyethylene n prffin wxes s ontrolle elivery systems for ifferent fertilizers. In. Eng. Chem. Res. 39: